Construction of screw-propelled ships.



' PATENTED APR. 14, 1903.

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No; 884,912; PATENTED APR. 14, 1908 J. T. -DUNGAN.

CONSTRUCTION OF SGREWPROPELLED SHIPS. v APPLICATION FILED mm; 22. 1907.

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/v v5 r0)? 1 w 1 771755 555 JOHN THOMAS DUNCAN, OF CARDIFF, ENGLAND.

CONSTRUCTION OF SCREW-PROPELLED SHIPS.

Specification of Letters Patent.

Patented April 14, 1908.

Application filed June 22, 1907. Serial No. 380,334.

To all whom it may concern;

Be it known that I, J OHN THOMAS DUNCAN, subject of King of Great Britain, residing at Mercantile Chambers, Docks, Cardiff, county of Glamorgan, England, have invented new and useful Im rovements in the Construction of Screwropelled Ships, of which the following is a specification.

This invention relates to improvements in the construction of screw-propelled ships. In such ships there is necessarily a tunnel extending to the stern of the vessel from the en gine room, in which tunnel is carried the propeller shaft, the tunnelbeing high and broad enough to be traversed with convenience. Consequently the portion of the hold in the stern of the vessel, up to the level of the roof of the tunnel, comprises two pockets from which any cargo carried therein cannot be removed with as great a facility as from the other cargo carrying portions of the ship. This is particularly true in the case of cargo carried 1n bulk as for example, coal and'grain.

The exigencies of ,the service of such vesselsnecessarily require them to perform a portion of their voyage, out or home, more or less completely without cargo and therefore with ballast substituted. The first function of the ballast is to immerse the ship sufficiently to provide arequisite degree of stability and secondly, due re ard being paid to the requirement of stabi ity, to preferentially immerse the stern end of, the Vessel and submerge as large a portion of the screw-propeller as possible. These considerations coupled with the fact that any low situated portion of the volume of the hold which is permanently devoted to the reception of water ballast is exempted from being included in the register of the ship, have led me to my invention which consists in extending the roof of the tunnel over the side spaces and thus to convert those spaces into permanent water-tight tanks and provide a continuous floor above those 45 tanks and the intervening shaft tunnel for the deposit of cargo which can be removed therefrom with the minimum amount of inconvenience.

The accompanying'drawings show the after portion 0 a ship constructed in accordance with this invention, in which Figure 1 is a part transverse section, and Fig. 2 is a longitudinal section taken along a vertical plane on one side of the shaft tunnel, and drawn to a smaller scale.

In these drawings a a are the sides of the shaft tunnel and b is its roof. The plating of this roof is made continuous from side to side of the ship for the entire portion of the length of the ship from the engine-room bulkhead g to the stern bulkhead h, the wing portions b forming the water-tight ceilings of ballasttanks 0 and c and carrying an uninterrru ted floor of a hold-space d'which extends Tom the after engine-room bulkhead g to the stern bulkhead h.

The section of the propeller shaft is represented by e and is shown situated somewhat V a correspondingly less capacity. The side spaces, which are thus converted into waterballast tanks, are subdivided both transversely and also lon itudinally as shown at The subdivision wilT enable any one or more of the compartments to be com letely filled with -water when only partia ballast is wanted and avoid the objection to the presence of shifting ballast such as would be the consequence of a partly filled tank in a sea-v way. The compartment construction also presents greateropportunities for adjusting the trim of the ship when the cargo is unship ed in an unsymmetrical manner. Furt er the partition walls of the compartments will serve to strengthen the floor of the hold (1 above. To compensate for the loss of cargo space thus devoted to the carrying ofv water-ballast and, in a manner which will enable the normal longitudinal distribution of. the weight in a fully laden ship to be retained, I find it structurally very advantageous to heighten the upper deck '6 in the after portion of the vessel thereby providing a quarter-deck i Besides the advantages above described, it will be apparent that. the continuous floor over the tunnel, having its edges united to the sides of the ship, will add greatly to its local structural strength and stiffness. Ships which have to perform voyages in heavy seas with the screw-propeller only partially submerged, to which ships the resent invention is intended to be appliec, are subject to somewhat excessive ocal dynamic stresses provision for which can be adequately and advantageously made by the modified construction which constitutes the embodiment of the present invention.

Claims.

1. In a screw-propelled ship, a shaft. tunnel, a roof to said tunnel extending to the sides of the ship, and permanent water ballast tanks on each side of said tunnel located beneath the extended roof thereof.

2. In a screw-propelled ship, a shaft tunnel, a roof to said tunnel extending to the sides of the ship, and permanent water ballast tanks on each side of said tunnel located beneath the extended roof thereof and between the after engine-room bulkhead and the stern bulkhead of the shi 3. In a screw-propelled ship, a shaft tunnel, a roofto said tunnel extending to the sides of the ship, permanent waterballast tanks on each side of said tunnel located beneath the extended roof thereof and watertight partitions in said tanks.

4. In a screw-propelled ship, a shaft tun.- nel, a roof to said tunnel extending to the sides of the ship, permanent water ballast tanks 011 each side of said tunnel located beneath the extended roof thereof and between the after engine-room bulkhead. and the stern bulkhead of the ship and. water-tight partitions in said tanks.

5. In a screw-pro mlled ship, a shaft tunnel, a roof to said tunnel extending to the sides of the ship, and, in the after portion of the ship, a quarter deck situated above the level of the upper deck of the vessel.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

JOHN THOMAS DUNUAN.

Witnesses H. NIXON, J. W. DUNCAN.

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